Of digital still cameras, products having a function capable of photographing at almost the same number of recording pixels as the number of effective pixels of an image sensing element and also photographing at a smaller number of recording pixels than the number of effective pixels become commercially available. As the number of pixels of an image sensing element increases year by year, comfortable photographing without any stress on the user requires an increase in speed at the building components of a digital camera, and also reduction in the data amount of a signal subjected to an image process in photographing at a smaller number of recording pixels than the number of effective pixels.
To meet this request, Japanese Patent Laid-Open No. 11-308560 proposes a method of achieving an image process and recording at high speeds by performing a reduction process for data of the Bayer array of an original image and obtaining data of a Bayer array with a smaller number of pixels. According to the method of the data reduction process disclosed in this reference, however, the barycentric positions of pixel signals of data of a Bayer array after the reduction process are localized, and an image obtained as a result of a subsequent signal process degrades, a detailed description of which will be omitted.
FIGS. 6 and 7 show an example of a conventional ¼ reduction process which degrades an image. FIG. 6 is a view showing the planar positions of data of a Bayer array of four G, R, B, and g colors before the reduction process. FIG. 7 is a view showing the planar barycentric positions of data after a ½ reduction process in the longitudinal and lateral directions.
The transformations of the conventional reduction process are given byG′1=(G1+G2+G6+G7)/4R′1=(R1+R2+R6+R7)/4B′1=(B1+B2+B6+B7)/4g′1=(g1+g2+g6+g7)/4
As shown in FIG. 7, the pitches between the barycenters of pixels of data after the reduction process are not equal.